6550 vs KT88 vs KT90


From what I hear, these tubes are interchangable on most amps it seems that the 6550 is the least loved tube of the bunch. What are the sonic differences of these tubes? Thanks in advance for your reply.
jman
I think they are both equally important. The most important aspect of a tube amp(in my experience) is the transformers. It is by far, the most expensive functional part of a tube amp. This is what separates Jolida from companies like Air Tight. Yeah, they both use the same tube type(EL34, and same tube once you retube the Jolida), but there is something that prevents you from attaining that same level of sound for the two. Transformers are as different as anything else in the amp. If we would allow that interconnects have a major effect on sound, then we also have to give transformers their due. They have several orders of magnitude more length than a 1 meter interconnect. Like most cables, most use different wire, and different construction. We also have to consider the circuit design, parts quality, etc.(things we NEVER mention with tube amps). That being said, we take tubes seriously because it is the one area of the amp we can control. Like different brands of gasoline yielding different performance in our cars(we can't change engines). We get different sounds from different tubes. Garfish, if you need to maintain the level of bass you are accustomed to, you need to look at amps with the larger tubes(6550/KT88/KT90). But, please go out and listen to an EL34 amp. There is a tube magic in many of them that is quite addictive. You may find yourself with two setups.
Great post Trelja! Hi to you too, Craig! I agree that the transformers must be an important aspect of tube amp designs. So much depends on an amp's ability to recover (and not introduce nasty harmonics in doing so) from transients / dynamics (even relatively low level ones). They really make or break an amp. Though my experience is fairly limited (own a Manley, owned a Jadis Defy7, and listened in my system to ARC VT100 MkII and VT200), I can't deny the magic I'm hearing through my EL34 based Manley amps, especially with the Svet EL34's. Craig, my good friend has a DNA2 LAE with Rev A from Steve McCormack. It is by any solid state standard a top notch amplifier IMHO. I LOVE that amp. In several ways, I felt it bettered the ARC VT200. However, after listening to my amps for a few weeks in his system, he is making the switch to tubes. It is definitely worth the experimentation to find a tube amp that "does it for you". Good luck and great thread! Jordan
Sorry Craig, forgot to comment on bass. I think the bass from the DNA2 is tighter, but not better. Oddly enough, when directly comparing the ARC VT200 to my friend's DNA2, I thought the ARC better portrayed the sound of a double bass and other low frequency instruments. I won't wax on the "magic" of my Manley's, but I'd say the ARC is better than my Manley's overall. Tube amps can do bass "right" in the right system! Hope it helps. Jordan
The "Electronic industry" (Ei), has been rebuilt, however, the economic "sanctions" are still in place, and who knows how long? I may be able to get some KT-90, and other Ei products. E-mail me with the questions if interested!
Thanks for the offer Eldragon! Ei tubes are available. In fact, Jadis informed me that they see no potential problems with supply. However, the sanctions will probably hurt us in the USA. No one will care because this is such a minuscule hobby. But, last year the price of a matched quad of KT90s was $96(in a Stereophile ad), within 2 months it went to $150. I am not sure where it is now, but buying from a high end dealer or Jadis will be over $500(as of February, 2000). I am just happy they supposedly last way longer than we usually expect tubes to last.